Exogenous NO Alleviates The Damage Of B[a]P Stress On The Growth,Absorption And Transport Of Mineral Elements Of Ryegrass

At present,with the economical fast development,environmental problems appear gradually.Industry and mining give us material wealth,but they also bring serious problems of pollution.Polycyclic aromatic hydrocarbons(PAHs)are one of the typical representatives of organic pollutants.They not only pollute soil,result in crop losses,but also endanger human health.Therefore,physiological mechanism for plants to adapt to PAHs is one of the important of ecological research.Benzo[a]pyrene(B[a]P)is one of the most toxic and strongest carcinogen of PAHs.It has stable chemical property and widely exists in water,soil and atmosphere.It can cause serious damage to the visceral organs and nervous system of animals,change the cell cycle and induce canceration of cells.B[a]P is representative in measuring PAHs level in monitoring environment.Therefore,it is of great significance for improving soil quality and ensuring environmental and ecological security to carry out B[a]P research.Nitric oxide(NO)is an important signal molecule in plants,involved in seed germination,growth,antioxidant,osmotic regulation,photosynthesis,signal transduction,gene expression and other metabolic processes.It has a positive effect on regulating plant environment stress such as heavy metals stress,low temperature stress,salt stress,drought stress etc.However,the effects of NO on the transport and absorption of mineral elements and heavy metals in plants under B[a]P stress have not been systematically explored.Therefore,the study of the effects of exogenous NO on plant growth,absorption and transport of mineral elements under B[a]P stress is of importance to improve the resistance of plants to PAHs pollution.To determine exogenous NO alleviates the damage of B[a]P stress on the growth,absorption and transportation of mineral elements of ryegrass(Lolium perenne L.),the effects of B[a]P(10,20,30,40?mol·L^-1)on seed germination,biomass,root vitality,nitrate reductase(NR)activity and absorption and transportation of mineral elements of ryegrass were investigated.The results showed that 30?mol·L^-1 B[a]P had both promoting and inhibiting effects on ryegrass.Then 30?mol·L^-1 B[a]P was mixed with different concentrations(100,200,300,400?mol·L^-1)of exogenous NO on seed germination,biomass,root vitality,NR activity and absorption and transportation of mineral elements of ryegrass.The results showed that:(1)Different concentrations of B[a]P(10-40?mol·L^-1)promoted the plant height of ryegrass.The fresh weight and dry weight of ryegrass firstly increased and then decreased with the increase of B[a]P concentration.Seed germination and root vitality of ryegrass were significantly inhibited with the increase of B[a]P concentration.The NR activity of ryegrass first increased and then decreased.And the inhibition rate of ryegrass germination index was 89.82%under 40?mol·L^-1 B[a]P treatment.The absorption of Cu and Cd decreased under the different concentrationsof B[a]P treatment,while the absorption of N,P,Mn and Pb transferred and concentrated in different parts with B[a]P concentration.10?mol·L^-1B[a]P treatment significantly promoted the absorption of P,Mn and Pb,20?mol·L^-1B[a]P promoted the absorption of K,30?mol·L^-1B[a]P promoted the absorption of N and Pb,but B[a]P stress had no significant effect on the absorption of Zn.(2)The various concentration(100-400?mol·L^-1)of exogenous NO promoted plant height and dry weight,and decreased fresh weight of ryegrass.The seed germination,root vitality and NR activity of ryegrass increased firstly and then decreased with the increase of exogenous NO concentration.N,P,Mn,Cu and Pb further transferred to the root system.300?mol·L^-1exogenous NO promoted the absorption of N and enhanced the transport capacity of N,Cu and Pb elements in ryegrass.400?mol·L^-1 exogenous NO promoted P by 64.80%,and enhanced the transport capacity of P,Zn and Mn.(3)Correlation analysis of elements in ryegrass showed that N,Zn,Mn,Cd were significantly correlated with physiological indexes of ryegrass.The correlation coefficient between plant height and N content in root was 0.939,and that between plant height and Zn content was-0.955.There was a significant negative correlation between Zn contentand NR activity and underground fresh weight in leaves of ryegrass.There was a significant negative correlation between Mn content and germination potential,and a significant positive correlation between Cd contentand ground dry weight,with a correlation coefficient of 0.938.Cluster analysis and principal component analysis showed that 200 and 300?mol·L^-1exogenous NO had the best effect on reducing the damage of B[a]P stress on the growth and mineral element absorption of ryegrass.